RFR: 8307423: [s390x] Represent Registers as values

[Amit Kumar]

On Thu, 4 May 2023 15:08:57 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

> The recent Register implementation uses wild pointer (including null pointer) dereferences which exhibit undefined behavior. We should migrate away from pointer-based representation of Register values as it was done for x86 ([JDK-8292153](https://bugs.openjdk.org/browse/JDK-8292153)). Problems exist when trying to build with GCC 11.3.0 ([JDK-8307093](https://bugs.openjdk.org/browse/JDK-8307093)).
> 
> Tested `fastdebug, slowdebug, optimized, release build` , `tier1-test` on fastdebug build and build with GCC-9.5.0 as well.

Hi @RealLucy, @TheRealMDoerr 

Please review the changes.
Thank you

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PR Comment: https://git.openjdk.org/jdk/pull/13805#issuecomment-1535002668